High Dynamic Range Displays Using Filterless LCD(s) For Increasing Contrast And Resolution

ABSTRACT

A display provides increased contrast and resolution via first LCD panel energized to generate an image and a second LCD panel configured to increase contrast of the image. The second panel is an LCD panel without color filters and is configured to increase contrast by decreasing black levels of dark portions of images using polarization rotation and filtration. The second LCD panel may have higher resolution than the first LCD panel. A half wave plate and/or film is placed in between the first and the second panel. The panels may be directly illuminated or edge lit, and may be globally or locally dimmed lights that may also include individual control of color intensities for each image or frame displayed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part (CIP) application andclaims the benefit of, and priority to, the following applications: (1)co-pending PCT/US2011/035915, filed on May 10, 2011 (2) which in turnclaims the benefit of co-pending application U.S. patent applicationSer. No. 12/780,749, filed on May 14, 2010; and (3) co-pending PCTapplication PCT/US12/27729, filed Mar. 5, 2012; (4) which in turn claimsthe benefit of U.S. Provisional Patent Application No. 61/450,802 filed9 Mar. 2011. The disclosure made in the application Ser. Nos.12/780,749, PCT/US2011/035915, PCT/US12/27729 and 61/450,802 are herebyincorporated by reference in their entirety.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to High Dynamic Range Displays (HDR), andmore particularly to HDR displays using dual modulation.

2. Discussion of Background

High Dynamic Range (HDR) displays are generally defined as having adynamic range of greater than 800 to 1. Recent advances in technologyhave produced displays claiming contrast ratios of more than 1,000,000to 1.

Generally speaking, these higher contrast ratio HDR displays utilizelocal dimming of the backlight that illuminates the LCD panel. An earlypatent in this area, U.S. Pat. No. 6,891,672, by Whitehead, Ward,Stuerzlinger, and Seetzen entitled “HIGH DYNAMIC RANGE DISPLAY DEVICES”describes the fundamental techniques. Such techniques includeilluminating the LCD panel with an approximation of a desired image andthen further modulating the approximation with the LCD panel so that itapproaches the desired image.

Other forms of improving contrast have also been presented, including“darkening” of an LCoS projected image through the use of an LCD panel(Berman), and the use of multiple registered modulating layers orpremodulators (e.g., Blackham U.S. Pat. No. 5,978,142, Gibbon U.S. Pat.No. 7,050,122, and others). However, commercially available HDR displayshave deficiencies in reproducing starfields and other challenging imagesmainly due to parallax, backlight leakage, and other issues, andartifacts resulting therefrom.

SUMMARY OF THE INVENTION

The present inventors have realized the need to improve spatiallylocalized contrast in LCD panels and other displays beyond existingattempts. In various embodiments, displays described in this documentcan be used for developing and commercializing a low costconsumer/prosumer grade high dynamic range display monitor. The hardwareelements and algorithmic components described in this document can bedeveloped into software plug-ins or as a software module in existinggraphics cards to perform relevant tasks to turn existing displays(changing existing designs and/or retrofits) into high dynamic rangedisplays.

In one embodiment, the present invention provides a high dynamic rangedisplay comprising a color LCD panel for generating an image (theimage-generating panel) and an LCD panel without color filters (thecontrast-improving panel) arranged to increase the contrast ratio andimprove black levels (either making them darker or increasing the colorand brightness fidelity of dark areas that are not intended to becompletely black) in the generated image.

In another embodiment, the present invention provides a displaycomprising an image-generating panel and a contrast-improving panelwherein the contrast-improving panel comprises an LCD panel withoutcolor filters. The contrast-improving panel may operate in combinationwith an analyzing polarizer. The contrast-improving panel may be placeddownstream of the image-generating panel. The resolution of thecontrast-improving panel may be higher or lower than theimage-generating panel. The image-generating panel may comprise, forexample, a color filter based LCD panel having the same polarizationrotating design as the contrast-improving panel. The contrast-improvingpanel may be, for example, abutted to the image-generating panel.

The invention includes a controller comprised of an image-generatingpanel energization module (e.g., a color module and/or a colorcorrection module) and a contrast-improving panel energization module(e.g., a contrast-improving control module). The controller may beconnected, for example, to energize both the image-generating LCD andthe contrast-improving LCD with control data produced by thecorresponding energization module(s). Energization of theimage-generating panel may be based in part on feedback from thecontrast-improving panel energization module to the image-generationpanel energization module.

The controller may be configured, for example, to input data from amedia source of a standardized high resolution and contrast, or higher(e.g., High Definition VDR), or other image types. The image-generatingpanel may be selected to be capable of producing an image of thestandardized high (or other) resolution. The contrast-improving layer isconfigured to increase contrast using, for example, a differentresolution than the image-generating panel. Preferably, the resolutionof the contrast enhancing panel is higher than the image generatingpanel (but may be equivalent or less).

The present invention includes a display comprising a contrast-improvingpanel, which may comprise, for example, an LCD panel without colorfilters. The display may include another modulators such as acolor-panel, and, the contrast-improving panel may have a higherresolution than the other modulator or modulators. The display mayinclude, for example, a set of diffusers, including a relatively coarsediffuser configured to diffuse light from a backlight of the display,and a relatively fine diffuser configured to mask high frequency detailsor uncontrolled features in light modulated by the contrast-improvingpanel. The contrast-improving panel may be located between the set ofdiffusers and upstream of the other modulator(s).

The present invention includes displays where the image-generating panelcomprises a color filter layer, an active layer, and a polarizationfilter layer, and the contrast-improving panel comprises an active layerand a polarization filter layer. The layers of the image-generatingpanel and the contrast-improving panel may be preferably arranged, forexample, so as to place the active layers of the image-generating paneland the contrast-improving panel as close together as possible.

The image-generating layer is backlit by at least one type of lightsource. The light sources may comprise, for example, of CCFLs, LEDs, andOLEDs. These may be directly illuminating or the light can be carriedthrough a light pipe, in the case of an edge lit configuration. In oneembodiment, the array of light sources comprises at least one of thefollowing: White or broad spectrum light sources, RGB light sources,RGBW light sources, RGB plus one or more additional primary lightsources, or other multi-primary light source color combinations. Thearray of light sources (e.g., edge-lit light sources) may be locallydimmed. In one embodiment, the light sources comprise different colorsand each color's brightness is individually controllable.

In one embodiment, the display includes a contrast-improving layer(e.g., contrast-improving panel) that is backlit by an array of lightsources, and the backlight and contrast-improving panels are arrangedsuch that light passing through the contrast-improving panel from thebacklight illuminates the image-generating panel. The contrast-improvingpanel may produce, for example, a base version of an image to bedisplayed by the display and the image-producing panel further modulatesthe base image to produce the image to be displayed. The base imagecomprises, for example, brightness intensity in proportion to brightnessintensities of the image to be displayed. The brightness intensity ofthe base image may be a sharper image than the image to be displayed. Inone embodiment, the base image is a blurred approximation of brightnesslevels in proportion to brightness levels of the image to be displayed.

In similar and other embodiments, the invention includes a controllerconnected to an image-generating panel and a brightness-improving paneland is configured to provide first-processed image data to theimage-generating panel and second-processed image data to thebrightness-improving panel, wherein the first-processed image data isproduced in part based on image data input from a media source andfeedback from production of the second-processed image data. Thefirst-processed image data may comprise a full-color high-resolutionversion of the input image data, and the second-processed image data maycomprise a mapping of brightness levels proportional to the input imagedata.

The invention may be implemented as a display or as a system andportions of the invention may be conveniently implemented as a method,for example, in programming on a general purpose computer, or networkedcomputers, and the results may be displayed on an output deviceconnected to any of the general purpose, networked computers, ortransmitted to a remote device for output or display. In addition, anycomponents of the present invention represented in a computer program,data sequences, and/or control signals may be embodied as an electronicsignal broadcast (or transmitted) at any frequency in any mediumincluding, but not limited to, wireless broadcasts, and transmissionsover copper wire(s), fiber optic cable(s), and co-ax cable(s), etc.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A is a schematic diagram of a high dynamic range display accordingto an embodiment of the present invention;

FIGS. 1B to 1D are a schematic diagram of high dynamic range displaysfurther comprising a half wave plate according to an embodiment of thepresent invention;

FIG. 2A is a schematic diagram of a high dynamic range display accordingto another embodiment of the present invention;

FIG. 2B is a schematic diagram of a high dynamic range display accordingto another embodiment of the present invention;

FIG. 2C is a graph illustrating high frequency features and diffusionaccording to an embodiment of the present invention;

FIG. 3A is a drawing illustrating an arrangement of layers in a typicalLCD panel;

FIG. 3B is a drawing illustrating an arrangement of layers in an LCDpanel and a brightness-improving panel according to an embodiment of thepresent invention;

FIG. 3C a drawing illustrating an arrangement of layers in an LCD paneland a brightness-improving panel further comprising a half wave plateaccording to an embodiment of the present invention;

FIG. 4A is an architecture and an alternative architecture of anelectronic device that generates energization signals for LCD panels andcontrast-improving panels according to an embodiment of the presentinvention;

FIG. 4B is an architecture of another electronic device that generatesenergization signals for LCD panels and contrast-improving panelsaccording to an embodiment of the present invention;

FIG. 4C is an architecture of yet another electronic device thatgenerates energization signals for LCD panels and contrast-improvingpanels according to an embodiment of the present invention;

FIG. 4D is an architecture of still yet another electronic device thatgenerates energization signals for LCD panels and contrast-improvingpanels according to an embodiment of the present invention;

FIG. 5 is a flow chart of a process for energizing a high dynamic rangedisplay according to various embodiments of the present invention;

FIG. 6 is an illustration of a color diagram describing aspects ofvarious embodiments of the invention;

FIG. 7A is an arrangement of controllable panels according to anembodiment of the present invention;

FIG. 7B is an arrangement of pixels on panels according to an embodimentof the present invention;

FIG. 8 is an arrangement of controllable panels according to variousembodiments, including simultaneous 2D and 3D displays, of the presentinvention;

FIG. 9 is a drawing of one possible embodiment of a simultaneous 2D and3D display according to the present invention; and

FIG. 10 is an arrangement of controllable panels according to anembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts, and more particularly to FIG. 1thereof, there is illustrated a new construction for a high dynamicrange display 100 according to an embodiment of the present invention.The display 100 includes a backlight 110 which may be a standard CCFL orother broadband lighting source (e.g., LEDs, OLEDs, etc.). In addition,the backlight may be direct lit (light source(s) directly illuminatingdownstream modulation panels) or edge lit (as is popular in many thinscreen LCD display designs). Further yet, the backlight may be constant,globally dimmed, or locally dimmed. The light source for this displaycan be white, controllable luminance, or multiple color driven.

The backlight 110 illuminates downstream modulators, including, in thisexample, an LCD panel 120 which modulates the backlight in intensity andcolor. A controllable polarizer (or contrast-improving panel) 130further modulates the light as to polarity (and which may then beattenuated by a polarization layer to effect an intensity modulation ofthe output light).

The LCD panel 120 is constructed to include an initial polarizing layer122, which may be for example, any of a reflective polarizer, anabsorptive polarizer, or a polarization converter, or another devicethat provides an initial uniform polarization orientation from whichdownstream modulations are to be based. Preferably, the initialpolarizing layer 122 is a reflective polarizer so that light that thereflected light may be “re-cycled” by reflection into and then back outof the optical cavity of the backlight 110. An active layer 124comprises liquid crystals (e.g., twisted nematic) and color filters(e.g., typically RGB). The liquid crystals are oriented based on anenergization of the active layer intended to rotate or changepolarization of light passing through the filters. A passivepolarization analyzer and/or finishing polarizer 126, which may be, forexample, an absorptive polarizing layer that filters out (or passes)light of a predefined polarization as changed by the liquid crystals.

The controllable polarizer (contrast-improving panel) 130, may be, forexample, the active elements of an LCD panel (e.g., a TN layer) combinedwith a passive polarizer (e.g., active layer, or active elements 134 andpassive polarizer 136). The controllable polarizer 130 may be, forexample, an LCD panel without color filters. As shown, the initialpolarizer of this second LCD panel may be removed, relying, in thisspecific case, on the passive polarizing analyzer 126 for an initialuniform polarization.

In the case of a constant backlight, the backlight 110 produces aninitial light 112 which is constant or uniform. In other embodiments,the initial light 112 may be modulated, e.g., any of spatially modulatedlight, pre-modulated light, globally dimmed light, individual RGBdimmed, temporally modulated light, or others, and/or a combination ofthe above. The initial light 112 illuminates the first downstreammodulator (note that additional optical elements may be placed atvirtually any point in the light/image chain, including any ofdiffusers, collimators, DEV, Brightness Enhancement Films (BEFs), etc).Other optical elements including reflectors may also be utilizeddepending on the design (e.g., side lit display designs may utilize, forexample, a reflector/diffuser combination to redirect and diffuse lightfrom a side light path that is mainly parallel to a display screen to alight path that is mainly perpendicular to the display screen.

The image-generating panel 120 modulates the initial light 112 in amanner that is physically similar to a standard LCD display. Theenergization of the image-generating panel 120 is calculated toaccommodate the design and use of the controllable polarizer 130 and isdiscussed in more detail further below. 1st modulated light 128 isemitted from the image-generating panel 120 and illuminates thecontrast-improving panel 130.

The contrast-improving panel 130 further modulates the 1st modulatedlight 128 in a manner that increases the contrast and, for example,resolution of the modulated light, resulting in a 2nd modulated light,or, in this case, better described as final image light 138. Theincreased resolution results, for example, when the contrast-improvingpanel 130 has more pixels for a given area than the image-generatingpanel 120.

Increased spatial resolution may also result when the active elements134 are of similar/same construction as active elements of theimage-generating panel 120 (e.g., LCD panel 120 and contrast-improvingpanel 130 are the same except that the contrast-improving panel 130 hasthe color filters removed). Benefits may also be obtained when thepixels of the contrast-improving panel are of a different shape, offset,size (e.g., smaller or larger), orientation (e.g., 0, 45, or 90degrees), or layout compared to the image-generating panel.

The active elements 134 rotate polarization of individual “pixels” ofthe 1st modulated light 128 based on a desired local dimming effect.Pixels in quotations because the pixels of first modulated light 128 maybe different from pixels of the active elements 134. In the case where adesign utilizes an LCD panel (e.g., LCD panel 120) having activeelements that are the same as active elements 134, the pixels of theactive elements 134 are still different from the pixels of the LCD panel120 because the pixels of the LCD panel 120 each include three activeelements (one for each Red, Green, and Blue filter that forms each LCDpixel), where each element of the active elements 134 may be defined asa single pixel.

The active elements 134 further modulate the 1st modulated light 128 ona pixel-by-pixel basis via the pixels of the active elements 134 byimposing a prescribed amount of polarization rotation. The modulation isthen effected by passive polarizer 136 that absorbs amounts of lightproportional to the light's difference in polarization as modulatedupstream. The contrast-improving panel 130 is shown downstream from theimage-generating panel 115, but may be placed upstream of theimage-generating panel 115.

Embodiments Comprising Half Wave Plate and/or Film

In the embodiments of FIGS. 1B, 1C and 1D, there is an optional halfwave plate and/or substrate comprising a half wave film depositedthereon (129). Without such a half wave plate, some embodiments of thepresent application may have one of the LCD panels re-worked in order toaffect an orthogonal polarization. Such a re-work may entail removingthe stock polarizing films of the LCD and replace them with new films toaffect the orthogonal polarization.

By placing half wave plate and/or film 129 in the optical path betweenthe two LCDs, this orthogonal polarization is achieved and the need tore-work one of the LCD panels is obviated.

In FIG. 1B, a polarization-preserving diffuser 131 a is placed upstreamof half wave plate 129. Placing a polarization-preserving diffuser inthe optical path with a half wave plate, somewhere between the first andthe second LCD panels may be desirable. For merely one example, such apolarization-preserving diffuser may help to minimize or eliminate anymoiré and/or any beat pattern that might arise due to the interaction ofthe cell structure located on the first and the second LCD. In addition,it may be desirable that the polarization-preserving diffuser has theproperty that it is strong enough diffusion to eliminate the visualmoiré between the two panels, but not too strong as to impact the localcontrast and efficiency of the optical stack due to depolarization.

Additionally, it may be desirable that the polarization-preservingdiffuser film alignment is chosen to minimize the birefringenceinteraction with the polarization direction, or a non-birefringencematerial is used.

As was mentioned, it may be desirable to have the diffuser somewhere inthe optical path between the first and second LCD panel. In FIG. 1C, itmay be seen that the diffuser 131 b is placed downstream of half waveplate 129. In FIG. 1D, it may be seen that the diffuser is combined insome manner (laminated, deposited, attached mechanically and/orchemically or the like) to the half wave plate itself. As alternativeembodiments, the diffuser may be located on either side of the half waveplate.

In one embodiment, a display may be constructed comprising a backlight;a first LCD panel which comprises a starting polarizer and a finishingpolarizer; a second LCD panel which also comprises a starting polarizerand finishing polarizer; and a half wave plate which is positionedbetween the first LCD panel and the second LCD panel. The first LCDpanel receives illumination from the backlight and modulates theillumination to form a first image. The half wave plate receives thefirst image and affects a polarization of this first image such that theresulting image comprises a polarization that is compatible with thestarting polarizer of the second LCD panel. In another embodiment, adiffuser layer and/or film (e.g., a diffuser that preservespolarization) may be combined with half wave plate 129 or the like—orsuch polarization preserving diffuser layer may be a separate opticalelement placed between the first LCD panel and the second LCD panel.Such polarization preserving diffuser layer may be positioned either infront of, or behind, the half wave plate.

In another embodiment, a display may comprise: a backlight; animage-generating panel; a contrast-improving panel; a half wave platepositioned between the image generating panel and the contrast improvingpanel; and a polarizing preserving diffuser positioned between the imagegenerating panel and the contrast improving panel. In variousembodiments, the display may further comprise having thecontrast-improving panel is placed downstream of the image-generatingpanel; the contrast-improving panel is placed upstream of theimage-generating panel. In various embodiments, it may be possible thatthe resolution of the contrast-improving panel is the same as theresolution of the image-generating panel; the resolution of thecontrast-improving panel is higher than the resolution of theimage-generating panel; or the resolution of the contrast-improvingpanel is lower than the resolution of the image-generating panel.

In other embodiments, the display may comprise a backlight being adirect lit backlight and/or an edge-lit backlight. The backlight maycomprise individually controllable light sources (e.g. LEDs, OLEDs,CCFLs or the like) where light sources may be controlled with respect tobrightness.

In other embodiments, the display may comprise image-generating panel tobe either a color panel or a greyscale panel. In addition, the displaymay comprise contrast-improving panel to be either a color panel or agreyscale panel.

FIG. 2A is a schematic diagram of a high dynamic range display 200according to another embodiment of the present invention. In FIG. 2A, acontrast-improving panel 240 (e.g., a controllable polarizer or modifiedcontrollable polarizer) is placed upstream of an image-generating panel250. Backlight 210 illuminates the contrast-improving panel with light218. The contrast-improving panel 240 produces modulated light 248,which is a locally dimmed version of the backlight 218. Modulated light248 is further modulated for color and brightness by a color panel 250(e.g., an LCD panel), producing final image light 258.

As shown, the contrast-improving panel 240 includes an initial polarizer242, and an active elements panel 242 (e.g., TN layer w/o colorfilters). The color panel 250 is constructed with a polarizer 246 (e.g.,an absorptive polarizer) which operates as both an initial polarizer forthe color panel and as an analyzer for the active elements panel 242. Acolor active layer 254 (e.g., TN layer+color filters) modulate the lightas to intensity and color, and a passive polarizer 256 effects themodulation by polarization based filtering.

FIG. 2B is a schematic diagram of a high dynamic range display 260according to another embodiment of the present invention. The display260 improves performance by the addition of appropriately designeddiffusers. The additional diffusers include an upstream diffuser 272 anda mid-stream diffuser 274. Upstream diffuser is a “rough” diffuser thatis designed to diffuse the backlight into an evenly distributed lightsource. In the case of locally dimmed backlight embodiment, the upstreamdiffuser is designed to cause the backlight to smoothly vary acrosspixels of the upstream modulator (e.g., contrast-improving panel 244 inthis example).

The midstream diffuser is specifically designed to smooth light emittedfrom the upstream modulator (e.g., contrast-improving panel 244 in thisexample). Preferably, the midstream diffuser operates to remove andsmooth rough edges of the lights emitted from each pixel of the upstreammodulator. To do so, the midstream diffuser is, for example, a diffuserthat is of higher diffusion resolution (e.g., diffuses smaller features)than the upstream diffuser and is capable of maintaining the modulatedresolution of light emitted from the upstream modulator. For example,FIG. 2C provides graphs that illustrate an approximate resolution ofmodulated light 280 in an on-off pattern as might be emitted from acontrast-improving panel or other upstream modulator. The midstreamdiffuser then operates to remove sharp edges and smooth the emittedlight while preferably maintaining as much peak brightness and darknessas possible as shown by diffused light 285.

Diffused light 285 takes away the sharp edges (e.g. higher frequencies)of the upstream-modulated light and is sufficient to “break-up” orprevent the formation of moiré patterns that typically develop asartifacts in displays with various combinations of grid like panelsand/or other optical elements. Also worth further discussion is that thediffused light 285 emitted from the mid-stream diffuser 274 ispreferably at an entirely different level of diffusion compared to thediffused light emitted from the upstream diffuser 272. The upstreamdiffuser may, for example, cause the backlight to smoothly vary from onelighting element in the backlight to the next. In contrast, themid-stream diffuser may, for example, provide smooth variances oflighting within a single pixel and mix light only from directly adjacentpixels. In one embodiment, the upstream and mid-stream diffusers differin diffusion coarseness by, for example, an order of magnitude or more.In fact, best results may occur with an even much greater differentialin resolution between the upstream and midstream diffusers.

In one embodiment, the upstream diffuser mixes and smoothes light frommultiple light sources in the backlight while the midstream diffusersmoothes light on the order of single contrast-improving size pixels. Inanother embodiment, the upstream diffuser may be described as mixinglight such that a single pixel of the upstream diffuser is illuminatedby a plurality of light sources in the backlight, and the mid-streamdiffuser may be described as mixing light on a sub-pixel level(sub-pixels of the upstream modulator). In one embodiment, the upstreamdiffuser is a rough diffuser compared to a relatively fine mid-streamdiffuser. In one embodiment, the mid-stream diffuser provides diffusionat less than a sub-pixel resolution. In another embodiment, themid-stream diffuser comprises a diffuser with a spatial transferfunction that either cuts-off, removes, repositions, or eliminates highfrequency elements of light that would otherwise be emitted. In anotherembodiment, the mid-stream diffuser may consist of a material thatdiffuses light more in one direction than in another to compensate forthe non-squareness of the upstream pixels.

In yet another embodiment, the mid-stream diffuser comprises a diffuserthat preserves enough detail such that the resolution of the modulatedlight is not altered (e.g., resolution not altered, but higher frequencydetails are no longer present). The mid-stream diffuser may be designedto mask high frequency details in the light modulated by thecontrast-improving panel. For example, the mid-stream diffuser maycomprise an optical low-pass filter that passes the lowest 4 harmonics(e.g., See FIG. 2C, the 4 lowest harmonics of 280 which approximatelyreproduces 285), but may be, for example, between 2-8 harmonics of thefundamental frequency. The mid-stream diffuser removes, for example,sub-pixel level features placed into the light stream by thecontrast-improving panel. In most embodiments, the size of a pixel inthe contrast-improving panel is smaller than a distance between theactive panels (e.g., distance between the contrast-improving panel andthe image-generating panel).

The coarseness of the mid-stream diffuser may, for example, bedetermined in part by a geometry of cells and surrounding areas of thecontrast-improving panel. For example, if the contrast-improving panelcomprises cells that are square with equivalent amounts of hardware(wires, cell walls, etc) on all sizes, then the coasrseness of themidstream diffuser would generally be uniform in all directions. If thecells of the contrast-improving panel are rectangular then thecoarseness of the midstream diffuser, assuming all other factors beingequal, would be coarser in the direction corresponding to the longerside of the rectangle and finer in the direction corresponding to theshorter side of the rectangle.

The coarseness of the mid-stream diffuser may also be determined, forexample, by a scale and/or physical or other measurable un-controlledfeatures and/or imperfections in the cells of the contrast-improvingpanel. The coarseness is determined at a resolution that masks theuncontrollable features but still allows the resolution of the panel (inthe form of modulated light) to pass mostly unaltered. For example,space between the cells of the contrast-improving panel may, forexample, block light or pass some amount of un-modulated light. Blockedlight or un-modulated light passed by the contrast-improving panelresults in an uncontrolled or un controllable in the image being formed.

Other uncontrollable features may include, for example, differences inmodulation in a cell not attributable to its energization level and/ornon-uniformity within a cell—any of which may be due to, for example,manufacturing or component quality variances. In one embodiment, thecoarseness of the mid-stream modulator is selected so that one or moreof the uncontrollable features are at least one of removed, masked, orotherwise minimized through diffusion. In one embodiment, theuncontrollable features are different depending on a direction (e.g.,horizontal and vertical), and each direction (at least two directions ina single diffuser) having different diffusion properties related to thedifferent amounts of uncontrollable features found in those directions.

Note that above, the polarizer 246 had been used as both an analyzer forthe up-stream modulator 244 and an initial orientation polarizer fordownstream modulator 254. The mid-stream diffuser 274 may be speciallyconstructed to include polarization or to maintain existingpolarization. In the case where mid-stream diffuser 274 maintainspolarization (e.g., a diffuser that does not substantially alter thepolarization of light being diffused), then polarizer 246 operates asboth the analyzer and initial orientation polarizer as described above.However, diffusers typically will impart more polarization alterationthan is desirable and therefore the addition of a polarizer to diffusionlayer 274 is desirable so that the light may be analyzed prior todiffusion and accompanying polarization changes. This additionalpolarizer will increase contrast at the expense of brightness. Thepresent invention includes designing a display for either increasedcontrast or brightness by respectively including or forgoing anadditional polarizer between active layers.

The embodiments of FIG. 1, FIG. 2A, and FIG. 2B are constructed so thatthe modulators (e.g., contrast-improving panel 240 and image-generatingpanel 250) are in close proximity to each other, which, as one benefit,reduces parallax caused by a separation between the panels. In thepresent invention, the modulators are sandwiched together eitherdirectly or separated by thin films, air gaps, or optical stack itemssuch as diffusers, collimators or other optical elements that arerelatively thin compared to glass and other layers of an LCD panel. Evenwith the close proximity of the panels, parallax may occur, particularlywhen difficult images or patterns are displayed and viewed at off-normalangles. The present inventors have realized that a specificconfiguration of panels brings the active layers of thecontrast-improving panel and the image-generating panel closer together,further reducing parallax effects.

Construction of a typical LCD panel 310 is illustrated in FIG. 3A. Afirst layer from the viewing side is a polarizing (analyzing) layer 312.Next, a relatively thick transparent substrate 314 (e.g., glass) isshown. Etched on the non-viewing side of the glass are, for example,wires and/or electronics for controlling a liquid crystal layer 316.Laminated together with the substrate and liquid crystal layer(s) is acolor filter layer 318 and an initial polarizing layer 320. Inoperation, a backlight illuminates the panel 310, polarizing layer 320sets an initial polarization, color filters 318 provide the primarycolors Red, Green, and Blue, and liquid crystal layer 316 rotatespolarization of each R, G, and B light by an amount that each light isto be attenuated. The analyzing layer then absorbs amounts of the R, G,and B lights based on their respective polarizations as imparted by theliquid crystal layer.

FIG. 3B is a drawing illustrating an arrangement of layers in animage-generating panel and a contrast-improving panel according to anembodiment of the present invention. The arrangement is specificallydesigned to place the active layer of a contrast-improving panel 350 asclose as possible to the active layer of the image-generating panel 370.

The layers of the contrast-improving panel 350 (from the backlight side)comprise a transparent substrate 352, an initial polarization layer 354,and an active layer 356 (e.g., controllable polarizing layer). Apolarizer 360 (which may be a separate component or laminated togetherwith either a contrast-improving panel 350 or an image-generating panel370) performs double duty as both an analyzing polarizer for thecontrast-improving panel 350 and an initial polarizing layer for theimage-generating panel 370.

Continuing from the backlight side, the layers of the image-generatingpanel 370 comprise a color filter layer 372, active layer 374, substrate376, and a polarization (analyzing layer) 378. Other arrangements of thelayers may be utilized, including, for example, placing the polarization(analyzing) layer 378 on the backlight side of the substrate 376. Thepolarization (analyzing) layer 378 may also be placed on the backlightside of the color filter layer 372 and the active layer 374 may beplaced as the first layer on the backlight side of the image-generatingpanel 370 (e.g., active layer-color filter layer-polarization (analyzinglayer).

In an embodiment of the present invention, a contrast-improving paneland an image-generating panel are provided from similarly constructedLCD panels. The contrast-improving panel may, for example, be orientedbackwards or upside down (flipped or inverted) relative to the LCDpanel. This arrangement places the active layers of thecontrast-improving panel and the image-generating panel closer togetherthan would be in the case of similarly oriented panels of typicalcommercially available construction.

FIG. 3C is yet another embodiment of a high dynamic display comprisingtwo stacked and/or laminated structures 380 and 390. A first stackand/or laminated structure 380 may comprise a half wave plate and apolarization preserving diffuser in order to match the two LCD panelswithout the need for re-working at least one of the panels as describedabove. In one embodiment, structure 380 may comprise reflectingpolarizer and/or DBEF film 381, initial polarizer 382, LCD panel 383,finishing polarizer 384, half wave plate 385 and polarization preservingdiffuser 386. In one embodiment, the rough surface of the diffuser maybe the exterior surface to the laminated structure—thus, giving a nicelamination to the structure.

An air gap may be present between the first stacked and/or laminatedstructure and the second stacked and/or laminated structure. The secondstack structure 390 may comprise an initial polarizer 391, an LCD panel392, a finishing polarizer 393 and an optional anti-glare layer 394.

In another embodiment, the polarization preserving diffuser should bestrong enough in terms of diffusion to eliminate potential moiré thatmight occur between the cell structure of the first and the second LCDpanels—however, the diffuser should not be too strong as to impact thelocal contrast and efficiency of the optical stack. Such impact mightarise due to depolarization of the light emanating from the firststructure and possibly filtered out by the initial polarizer of thesecond structure. This may also be desirable whether or not the displayis constructed with discrete layers (e.g. in FIG. 1B, 1C or 1D) or in alaminated structure (e.g. FIG. 3C).

In addition, the polarization preserving diffuser alignment may bechosen such that said polarization-preserving diffuser comprises adiffuser that substantially minimizes the birefringence interaction withthe polarization direction. Such a diffuser may have no birefringenceinteraction at all.

FIG. 4A provides an architecture of an electronic device 400 (e.g.,electronic circuitry, software architecture, programmable devicearchitecture, plug-in, etc., or combinations thereof) that generatesenergization signals for image-generating panels and contrast-improvingpanels according to an embodiment of the present invention. A signalcomprising, for example, RinGinBin, is provided and/or extracted from animage or video source (e.g., DVD, Cable, Broadcast, Satellite, Streamingvideo, Internet, removable media, thumb drive, etc.) to an LCD ColorCorrection module 410 and a Polarization Control module 420. Thepolarization control module prepares a Pout signal 425 that is connectedto a contrast-improving panel (e.g., controllable polarization panel).In essence, the Pout signal 425 indicates which pixels of thecontrast-improving panel should be attenuated and the amount ofattenuation. When using a controllable polarizer as thecontrast-improving panel, this is performed, for example, by rotatingthe polarization of pixels to be attenuated by an amount proportional tothe amount of desired attenuation for that pixel. The Pout signal 425may be, for example, a luminance calculation from a desired imagedefined by the RinGinBin data.

Processing in the Polarization Control Module, may include, for example,both a characterization that produces a corrected response curve (e.g.,correcting RGB values for a given luminance) and a non-linear function(e.g., transfer function) that increases or decreases local contrast(makes pixels darker or lighter). The non-linear function may, forexample, brighten or darken pixels in a manner that take into accountthe relative brightness of neighboring pixels. As shown, Pout is thenforwarded (fed into) the LCD Color Correction module 410 (via line 422).Alternatively, intermediate data may be exclusively or additionallyforwarded to the LCD Color Correction module (via 424). The intermediatedata, may be, for example, partially processed data including any one ormore steps performed to produce Pout (e.g., characterization withoutapplying the non-linear function).

Along with the RinGinBin data, the LCD Color Correction module preparesan RoutGoutBout signal 430 that is connected to control animage-generating panel (e.g., an LCD panel). The image-generating panelmay be an LCD display, plasma display, or other type of display device.

In another embodiment, an electronic device 440 (e.g., electroniccircuitry, software architecture, programmable device architecture,plug-in, etc., or combinations thereof) that generates energizationsignals for image-generating panels and contrast-improving panelsaccording to an embodiment of the present invention. A signalcomprising, for example, RinGinBin, is provided from an image or videosource (e.g., DVD, Cable, Broadcast, Satellite, Streaming video,Internet, removable media, thumb drive, etc.) to a Polarization ControlModule 442 and an LCD Color Correction module 446. The PolarizationControl Module 442 controls, for example, a polarizer that is physicallylocated in a display and upstream of a corresponding color panel. ThePolarization Control Module 442 may be configured to prepare modulationsignals for a higher resolution than the resolution of the color panel(e.g., higher resolution in the number of controllable pixels and higherresolution in the total number of controllable elements in a given areaof the corresponding panels). The polarization control module may beconfigured, for example, to control the active elements of a 1680×1050active element panel.

An output luminance Pout 442 is produced. In turn, an LCD ColorCorrection module 446 provides signals to control the correspondingcolor panel, which may be, for example, a 1920×1080 panel. The LCD ColorCorrection module 446 utilizes the video-in (RGB) signal plus resultsfrom the Polarization Control Module (e.g., luminance controlled by theupstream panels).

FIG. 4B is an architecture of an electronic device 450 (e.g., electroniccircuitry, software architecture, programmable device architecture,plug-in, etc., or combinations thereof) that generates energizationsignals for image-generating panels and contrast-improving panelsaccording to an embodiment of the present invention. A sourceimage/video signal comprising, for example, RinGinBin, is provided animage or video source (e.g., DVD, Cable, Broadcast, Satellite, Streamingvideo, Internet, removable media, thumb drive, etc.) to a globalbrightness computation module 452, which separates the light into itsprimary color components (e.g., R, G, and B) and provides thatinformation to a backlight controller 454. A backlight control signal isgenerated, which may be, for example, a globally dimmed backlight valuethat is calculated (e.g., for each primary color value), whichcomprises, for example, an energization amount (or intensity) ofindividual primary colored lights in a backlight 456. The backlight isthen energized according to the calculated backlight values for eachprimary.

In one embodiment, in the case of a locally dimmable backlight (e.g., abacklight that includes locally dimmed (or dimmable) light sources), thebacklight controller may generate a spatially modulated backlight thatilluminates downstream panels according to relative brightness in areasof the image (e.g., areas comprising, for example, each backlightpixel). The relative brightness may be computed, for example, based onthe relative intensities of each primary color in a correspondingbacklight pixel. Production of the spatially modulated backlight mayalso include, for example, consideration of the brightness ofneighboring or nearby backlight pixels, and/or, in the case of video,brightness of pixels in preceding and/or subsequent image frames.

A Dimming/Polarization Controller 458 receives the backlight controlsignal and the input video/image signal, which are utilized to produce acontrast-improving control signal. The contrast-improving control signalspecifies an amount of dimming produced by a contrast-improving panel460. In various embodiments, the contrast-improving panel is of higherresolution than the image-generating panel (e.g., LCD panel) and mayproduce, for example, a very precise illumination profile.

In one embodiment, the image-generating panel is downstream from thecontrast-improving panel and the higher resolution contrast-improvingpanel is utilized to produce an illumination profile that isintentionally blurred (blurred using the higher resolution capabilitiesof the contrast-improving panel as opposed to blurred because thecontrast-improving panel is of lower resolution). The intentionallyblurred image is blurred using the higher resolution capabilities of thedisplay separate and apart from any blurring that occurs among or due tomixing of the backlights due to point spread functions or otherqualities/orientations of the backlight or individual lights in thebacklight. Although the aforementioned blurring is separate and apartfrom backlight blurring or mixing, embodiments of the invention maynonetheless include amounts of mixing or blurring of individual elementsof the backlight.

A Color LCD Controller 462 receives the contrast-improving controlsignal, the backlight control signal, and the image/video signal whichare utilized to produce an image-generating control signal thatspecifies the energization of the color panel 485 relative to theupstream illumination (e.g., in various embodiments the combinedbacklight and contrast-improving panel produce the upstreamillumination) provided to the color panel 464.

FIG. 4C is an architecture of controllers according to an embodiment ofthe present invention. An RGBin signal is provided to both aPolarization Control Module 466 and an LCD Color Correction Module 468.The LCD Color Correction Module may be configured to correct and producean output for a 1920×1080 array of RGB pixels. The Polarization ControlModule may be configured to control other resolutions, for example,1680×1050 polarization cells.

The Polarization Control Module outputs to each of: the LCD ColorCorrection Module, a sub-pixel Interpolation and Registration module,and a filtering module. The sub-pixel interpolation module interpolatesvalues for each pixel of the polarization control panel (e.g., eachpixel may be considered a sub-pixel relative to the larger pixels of theimage-generating panel). The interpolation and registration moduleallows the embodiment to handle multiple panels with different controlresolutions and sizes. The spatial and range filtering module allows usto smooth the energization on the contrast-improving panel to get betterviewing angle performance while maintaining edges and preserving thehigh frequency details in the image. This module also enhances the localcontrast of this embodiment.

Filtering is performed based on the polarization control and precedingsub-pixel operations. The result is a P1, P2, and P3 output forcontrolling the controllable polarizer, and an output for controllingthe color panel.

FIG. 4D is an architecture of controllers according to an embodiment ofthe present invention that provides a framework for utilization of aHigh Dynamic Range (HDR) signal. The HDR signal could comprise an imageand/or images (e.g., video) having a dynamic range that is equivalent tothe dynamic range of the human visual system (HVS) on average. Since, onaverage, the HVS has greater dynamic range than most displays, a tonemapping algorithm is utilized to change the dynamic range of theimage(s) or portions of the images so that they are within luminancerange of the proposed display system. An HDR frame sequence {XinYinZin}is provided to a Global Tone Mapping Module 482, which outputs an RGBsignal which is then fed to Polarization Control and LCD ColorCorrection Modules.

FIG. 5 is a flow chart of a process for energizing a high dynamic rangedisplay according to various embodiments of the present invention. Atstep 510 Image and/or video data (the method repeated in real time foreach frame) is received. Luminance values are extracted from the imagedata and used to drive a contrast-improving panel (see step 520). Animage-generating panel optically co-joined with the contrast-improvingpanel is driven based on the image data and the global or local dimminglevels (step 530), or constant values representing the backlight color.

More details on a specific algorithm for driving the contrast-improvingand image-generating panels are now discussed for producing a pixelaccurate dual modulation displays. The architecture of two modulators ofperhaps similar construction allows performance of local dimming in asub-pixel (or higher resolution) fashion. Additionally, one of themodulators could have a different or the same resolution than the otherin either dimension.

Pixels in the contrast-improving panel can be driven based on theluminance of a corresponding (or related) input pixel. Thecontrast-improving pixel may be a sub-pixel of an input pixel, a portionof an input pixel, or a pixel optically and precisely corresponding toan input pixel. Accurate characterization of the local dimming panel'soutput luminance response could be used to map the input RGB pixelvalues to a specific drive level (e.g., specific polarization rotationin this example).

Drive values may be provided, for example, via:

Y _(max) =Y _(R) +Y _(G) +Y _(B)

Y _(out) =Y _(R) *R _(in) +Y _(G) *G _(in) +Y _(B) *B _(in)

drive_(polarizer) =f ₂(f ₁(Y _(out) /Y _(max)))

The function f₁ is the polynomial characterizing the luminance responseof the combined dual modulation system while linearly varying the localdimming panel's (polarizer's) control with the RGB color LCD drive isset to full white (maximum codewords).

The function f₂ a nonlinear transfer function that could represent theskew of the codewords with the luminance representing the nonlinearnature of the drive. The function could be approximated with either asimple gamma curve or a polynomial function. This drive computation canbe used to calculate the drive for pixels of the contrast-improvingpanel (sub-pixels (P1, P2, P3) of input pixels in the case where thecontrast-improving panel has a similar construction and orientation tothe image-generating panel). This function could also be used to improvethe local contrast of the display using a nonlinear input-outputrelationship making dark regions darker and bright regions brighter.

The interaction between the image-generating panel and thecontrast-improving panel (e.g., controllable polarizer) is representedin the color correction function. This function may utilize, forexample, surfaces mapped from the characterization of the colorprimaries of the image-generating panel with the corresponding amount oflocal dimming (e.g., polarization) from the contrast-improving panel.

The resulting RGB drive may, for example, be calculated as follows:

R _(out) =f ₃(R _(in) ,f ₄(R _(in) ,Y _(out)))

G _(out) =f ₅(G _(in) ,f ₆(G _(in) ,Y _(out)))

B _(out) =f ₇(B _(in) f ₈(B _(in) ,Y _(out)))

Here, f₄ f₆ and f₈ define the characterization functions that define theoutput primary for an input primary pixel values and a computed Y_(out),f₃, f₅ and f₇ define the nonlinear combination functions for combiningthe input primary and the output from the characterization functions.

The polarization control could be pre-computed in the LCD correctionsystem to drive the LCD control plane independent of the polarizationcontrol signals computed in the dimming plane drive.

Sub-pixel control of the contrast-improving panel can be used to smoothout any parallax errors that are incurred by it use. Since sub-pixelcontrol increases the implied resolution of the local dimming panel(e.g., polarizer), smoothing/dithering operations shall be more refinedand accurate. By using a smoothing mask on the drive image to themodulating polarizer, such as, for example:

[drive_(polarizer)](i,j)=f _(int R)(drive_(polarizer)](i,j))

where f_(int) is the smoothing operator applied on a spatial radius of Rsub-pixels. In a construction with 4 sub-pixels on the polarizercorresponding to every pixel on the color RGB LCD, the applied quaddesign would increase the resolution of the contrast-improving panel totwice that of the image-generating panel along both the width and theheight directions.

In an embodiment, a source image may be processed through a nonlinearfunction to modulate the contrast-improving panel. This can create aperceived effect of contrast stretching. Existing tone mappingalgorithms rely exclusively on software algorithms to stretch contrast.By using, for example, a design such as shown in FIG. 1, with thealgorithmic elements described above, contrast stretching without tonemapping or other contrast synthesis may be achieved.

The present invention also may be utilized for maintaining constantgamut over a wide range of luminance values. An expected representationof the chromaticity (x, y) for different luminance values follows asurface outlined the first drawing. However, the measured luminance of astandard display at the maximum codewords for the primaries creates aninclined top triangle as outlined in the first drawing.

However, some display systems demonstrate a gamut limiting effect asdescribed by the bottom figure. The projection of the color gamut ontothe chromaticity axes (x, y) is reduced in area for higher luminancevalues until it reduces to a single point at maximum drive values forthe individual color primaries (R=G=B=1.0 in normalized drive values).This point is usually the white point of the system.

By using a non-uniform current drive for the 3 primaries, the maximuminput codewords for the individual primaries can give us a flat-toppedtriangle at the higher luminance levels there by increasing the colorgamut and making the system demonstrate a more uniform projection on thechromaticity plane at higher luminance values (See FIG. 6, comparison ofcurrent system 610 and “ideal” system 620).

The present invention includes the use of RGB individually controlledtristimulus based backlights (e.g., LEDs, arranged in, for example, anedge lit configuration, direct lit array, or other arrangement). Byscaling the current drives to the RGB individually controlledtristimulus LED backlight, the 3D surface of the luminance vschromaticity of colors that represented may be adjusted. Luminancecontrol is primarily from the dimming plane and the combination of theLED backlight and the dimming plane, scaling the color drives to theLEDs allows for wider color gamut at higher luminance values. For atarget display luminance, the luminance vs current characterizationcurves may be used to determine/create the right scaling parameters fora current drive designed for better control of color gamut at thattarget luminance. This forms a basis for a global backlight controllerembodiment.

The global backlight controller embodiment can be used, for example, ona plurality of LEDs which are closely spaced to create an edge lit zonaldimming backlight on conjunction with the color LCD and the dimmingplane. By working on a plurality of LEDs at a time, the global backlightcontroller embodiment can also be used for correcting drifts in theoutput wavelength of light from a zone with luminance and maintain moreaccurate color properties at higher wavelengths.

The present invention includes computation of a color primary rotationmatrix from a sparse data set. Given a sparse set of tristimulusprimaries (R, G, B) as input images to the display system and theircorresponding luminance (Y) and chromaticity coordinates (x, y), wecould arrive at the optimum color rotation matrix for converting the RGBvalues to their corresponding XYZ values on the concerned display in thefollowing manner:

A=[P1P2P3 . . . Pn]T

where Px=[R G B]x for the x input sample primaries

B=[M1M2M3 . . . Mn]T

where Mx=[X Y Z]x for the x output luminance/chromaticity

For example, let the color rotation matrix be:

$X = \begin{bmatrix}{RX} & {RY} & {RZ} \\{GX} & {GY} & {GZ} \\{BX} & {BY} & {BZ}\end{bmatrix}$

This could be expressed as a linear system of equations of the form:

Ax=B

and compute the rotation matrix x using the pseudo-inverse as:

x=(A ^(T) A)⁻¹ A ^(T) B

This computed color rotation matrix would be optimized for minimum leastsquare color distorting in the XYZ space given the number of sample datapoints that we have captured. Given more uniformly spaced data points,the computed color rotation matrix would be a more accuraterepresentation of the true rotation operation by the display.

The present invention includes extending viewing angles inmulti-modulated display systems. The use of existing LCD panels withoutred, green or blue color filters allows for much greater resolution ofcontrast enhancement as used as a background or foreground panel withanother panel. This extra resolution becomes even more important whenthese dimming panels are coupled with different resolution color LCDpanels or with similar scaled color LCD panels, as it allows foradjustable viewing angles across the display with minimized visualartifacts.

In the case where the base panel has the pixels (e.g., sub-pixelscompared to other modulators in the same image chain) in clusters offour in a square configuration (2×2), even greater control is possibleas this doubles the pixel/sub-pixel resolution in both horizontal andvertical directions. Existing image processing techniques for imagescaling can be applied to these sub-pixel dimming regions if treated asindividual control points, allowing for variable viewing angles anddistances. To widen viewing angles as to accommodate multiplesimultaneous viewers, a Gaussian or similar low pass filter can beapplied as indicated by the spatial and range filtering embodiment inFIG. 4D.

The present invention includes controlling backlights for constantcolor. Traditional methods for setting display backlight light levelsand color involve selecting from a set of voltage or current levels thatdrive the light. These do not factor in the changes to the color orluminance due to component or environmental temperatures, component age,or other factors. Our method of backlight control involves sending tothe display a target color and luminance (usually with a scaled RGBtarget value), which is then compared with the values coming from acalibrated light and color sensor that is directly coupled with thebacklight, with corrections made using a feedback loop. This eliminatesthe warm-up time for the display to settle to a particular color, andany color or brightness drift over time. This feedback process can beaccelerated by using a feed-forward feedback hybrid driver (for thepurpose of real-time backlight changes). This allows the backlight toinstantly respond to control changes while still maintaining theprecision maintained by the color and light sensors.

The present invention may be implemented in a number of forms includingcombinations of hardware and processes described here and above. Anotherexemplary embodiment of a display device according to an embodiment ofthe invention is illustrated in FIG. 7A. A backlight 705 includes areflective polarizer 710 that produces backlight 715. The reflectivepolarizer reflects and polarizes light that is directed toward thebacklight's reflective polarizing surface(s). Such reflections includelight that has been bounced back to the backlight from a reflectivepolarizer 725 because it was not of the desired orientation for furtherdownstream processing by the display. Further reflection by thereflective polarizer changes the reflected lights polarization providingit another opportunity to pass the reflective polarizer 725 and beutilized in production of a desired image.

A diffuser stack 720 smoothes and diffuses the backlight 715, and thereflective or other type of polarizer passes light of a desired initialpolarization for further downstream processing. A contrast-improvingpanel 730 (e.g., controllable “sub-pixel” polarizer—again “sub-pixel”because the pixels of the contrast-improving panel may be of higherresolution than its corresponding (e.g., downstream) image-generatingpanel) either locally dims or further locally dims (further locally dimsin the case where backlight 710 is itself locally dimmed) light in theimage/light chain from backlight to viewer. A diffuser stack 735diffuses the locally dimmed light, and a image-generating panel 740(e.g., LCD panel) imparts final modulation (e.g., color, brightness, andspatial resolution) into the light, which is then emitted for display toa viewer. A polarizer (usually absorptive) is included in front of theimage-generating panel to realize the modulation imparted by the colorpanel. Additional anti-glare or other light processing layers may bepresent in front of the image-generating panel.

The discussion on pixels is now elaborated with reference to FIG. 7Bwhich provides a diagram illustrating a possible relationship betweenpixels of an image-generating panel and pixels of a contrast-improvingpanel. An image-generating panel 750 includes sets of Red, Green andBlue (RGB) controllable elements each comprising a pixel of the colorpanel. For example, one pixel is defined as colorLCD(i,j), where I and jidentify, for example, a row and column position of the pixel or RGBtriad comprising the pixel. In this case, a similar location may beidentified in the contrast-improving panel 780, where a set of threepixels corresponding to the RGB triad of colorLCD(i,j), P1, P2, and P3of a group of local dimming pixels identified as polarizer(i,j)(however, P1, P2, and P3 may also be appropriately referred to assub-pixels as they optically correspond to (or modulate) sub-pixelregions of the colorLCD pixels).

The present invention includes the use of modulators having differentresolutions. In such cases it may not be possible to align pixels of thecolor and dimming panels as illustrated in FIG. 7B (however, alignmentis not necessarily the case even when there is a direct correspondencebetween the size and arrangement between pixels of the local dimmingpanel and pixels of the color panel). Still, the pixels of thecontrast-improving panel may be referenced as pixels of thecontrast-improving panel or as sub-pixels of the color panel when theyare of smaller size or greater resolution than the color panel pixels,which they jointly modulate to produce an image.

The invention may be further extended to displays with additionalmodulators. For example, a display with 3 modulating panels andtechniques for driving the panels. By placing an additional controllablepolarizer in front of the design discussed and illustrated in FIG. 7,light at an output of the display could be steered at differentpolarization angles, ether in a linear or circular manner. By using thissystem in conjunction with 3D polarized glasses, we could steer theobjects on the display to either left or right eyes based on themodulation drive for the 3rd polarization panel. Thisstereoscopic-driving layer can be driven in various means using spatial,temporal, or color based stereoscopic methods along side traditionaltwo-dimensional content, alone or simultaneously.

In FIG. 8, a display 800 includes all of the proposed parts associatedwith the FIG. 7 embodiment, with an additional controllable panel 810.The additional controllable panel may be, for example, a controllablepolarizer similar in construction to the exemplary controllablepolarizer described with respect to local dimming panel 730. However,here the panel is controlled to output images for respective channels.The channels may be, for example, a left eye viewing channel or a righteye viewing channel that may be separated for viewing by viewing glasses815 that include different filters for the left eye and right eye.

For example, display 800 could be energized to alternately display aleft view and a right view of a 3D image. The images would then beseparated into different corresponding viewing channels by energizingthe additional controllable polarizer to polarize each of the imagesconsistent with its viewing channel. For example, in a left and rightpolarization viewing system, the glasses 815 could be constructed toinclude a P polarization filter on the left eye lens and an Spolarization filter on the right eye lens. In such a case, controllablepanel 810 is energized to pass/convert light modulated with left imagedata to a P polarization and pass/convert light modulated with rightimage data to S polarization. In another example, the light maymodulated with left or right image data in sections (e.g., light beingemitted from the display at any given time contains parts of both a leftand right channel image), and the controllable polarizer panel is alsoenergized in sections and synchronized with the displayed image sectionsto convert those sectional images to the appropriate polarization andsubsequent viewing through polarized filters by the left and rightviewing channels.

Beyond 3D, the configuration of FIG. 8 allows the design to be extendedto either more color accurate HDR or a 3D HDR display system. Inconjunction with a method to drive the accurate compensate for colorperformance in 2D and 3D modes, a passive 3D display results. Inaddition, a hybrid 2D/3D display may be implemented (either driving theadditional modulator for 3D channel separation, or to further refine a2D image). To create a quality image, color and brightness correctionmay be performed over the total image areas. The display can beswitchable between 2D and 3D operations, and can be configured tosimultaneously drive 3D and 2D on the same screen. As 3D images aresplit between two eyes, they tend to be less bright. Additional colorfilters can be applied to the 2D image areas so that both 3D and 2Dareas appear as the same brightness. Possible color correction can beapplied as well.

In one embodiment, the additional controllable panel 810 is utilized forboth 2D and 3D displays, and for providing a completely black borderaround the simultaneously displayed 2D and 3D images. As shown in FIG.9, a display 900 is energized to provide a 2D display area 902 and 3Ddisplay area 903. In the 2D display area 902, the additionalcontrollable panel 810 is utilized to enhance the dynamic range andblack levels of the 2D display. Simultaneously, in the 3D display area903, the additional controllable panel 810 is utilized to steerpolarization of the left or right channel image being displayed to apolarization consistent with the corresponding left or right viewingchannel. Finally, in border areas surrounding the 2D and 3D displayareas, the additional controllable panel 810 is utilized to increaseblackness (e.g., making a black boarder darker) or otherwise enhance theborder area.

Variances in any particular 3D implementation may include, for example,a mix of shutter styles, per pixel steering, and brightest areachroma-based techniques, alongside 2D images as well. For example, forshutter style, one embodiment alternatively displays left and rightimages with steering of entire image to left or right eye withpolarization layer (albeit at a reduced, or ½ frame rate). For a pixelsteering embodiment, where left and right images differ, steering may beperformed at alternate pixels to one eye or the other (albeit at areduced, ½ resolution per image). In a brightest area embodiment, eachpixel from both eye's images you find the highest luminance, then usingthe delta luminance between the two images steer the right lightproportion to both eyes (albeit at a reduction of color resolution inthe dimmer channel).

FIG. 10 is an arrangement of controllable panels 1000 according to anembodiment of the present invention. A backlight 1005 provides polarizedlight 1010 used to illuminate downstream panels. The backlight may be,for example, a polarized light source, an unpolarized light source withpolarization converting layers, and/or various combinations of optics,sources, films, and converters that ultimately produce the polarizedlight 1010. Typically, the backlight preferably includes a reflectivepolarization or a scattering layer for, for example, any of recycling,re-polarizing, de-polarizing, and/or redirection of stray lights orreflected lights toward (or back toward) the downstream panels. Suchfunctions of the panel may be selected on a case-by-case basis dependingon other factors of a particular design.

The backlight may include, for example, optics, louvers, light guides,or other devices (not shown) that are utilized to help align thepolarized light 1010 so that individual rays are parallel. A backlightdiffuser 1015 mixes and homogenizes the polarized light removing, forexample, local non-uniformities in intensity.

A first biasing polarizer 1020 sets the polarization of downstream lightto a first reference polarization. The reference polarization is usedfor downstream modulation provided by a first modulating panel, e.g.,LCD panel without color filters 1025.

An optional first analyzing polarizer 1030 is utilized, for example,when the LCD panel without color filters only changes polarization oflight rays to be modulated, the first analyzing polarizer then effectsthe modulation intended to be imparted by those polarization changes. Inother embodiments, the first analyzing polarizer may act as more of aclean-up polarizer removing unwanted stray polarizations or simplyfilter out light intended to be removed by the preceding LCD panel(e.g., reflected by a polarizer in the LCD panel).

A sub-pixel scaled diffuser 1035 mixes and diffuses light passed by thefirst modulating layer (panel 1025 and optional polarizer 1030). Bymaking the diffuser sub-pixel scaled, diffusion only occurs at thesub-pixel level or has minimal diffusion amongst neighboring pixels (butsignificant diffusion between sub-pixels). In lower resolution versionsof the invention, the diffuser may be designed to diffuse between alimited set of pixels (e.g., blocks of pixels such as 4 or 9) pixels.The sub-pixel scaled diffuser 1035 maintains the specific modulationintended for each pixel, and may be designed to maintain polarization.

A second biasing polarizer 1040 sets the polarization of downstreamlight to a second reference polarization. The second referencepolarization is used for downstream modulation provided by a secondmodulating panel 1045, e.g., 2nd LCD panel with color filters removed.An optional second analyzing polarizer 1050 performs a similar functionas analyzing polarizer 1030 and is a final polarization/analysis devicein the illustrated example.

Resolution of the modulating panels may be the same. In one embodimentthe first modulating panel is of lower resolution compared to the secondmodulating panel. In one embodiment, the first modulating panel hasgreater resolution than the second modulating panel.

A display according to the invention may further comprise an opticalstack including a reference polarizer (e.g., first biasing polarizer1020 or second biasing polarizer 1040) and a series of films configuredto enhance brightness and reduce loss of light transmitted through thestack. The films may include, for example, at least one brightnessenhancing layer, and may be designed to maintain polarization.

The optical stack may be positioned after a source of the locally dimmedlight and before a first of the downstream modulators, or betweendownstream modulators, or both (e.g., an embodiment having duplicate orsimilar optical stacks). In one embodiment, the stack comprises abacklight resolution scale diffuser where the backlight resolutioncomprises a resolution of a local dimming capability of a source orsources of the locally dimmed light (a stack that would be placedbetween the backlight and first downstream modulator, for example). Inanother embodiment, the stack comprises a sub-pixel scale diffuser wherethe sub-pixel scale corresponds to sub-pixels of an upstream modulator.

A sub-pixel scale diffuser may comprise, for example, a diffuser thatdiffuses sub-pixels proportional to sub-pixels generated by an LCD panelwith color filters removed. In one embodiment, subpixels of themodulator each comprise approximately ⅓ of a standard LCD pixel (whichmay be, for example, a “stripe” or “row” of individually controllableliquid crystals across a pixel).

A processing device 1055 receives a video or image signal and producesenergizing signals for the first and second modulating panels and mayalso be produced to control local and/or global dimming of thebacklight. The energizing signals may be produced exclusively from theimage signal, or may incorporate one or more of light field simulationsbased on the backlight (or energization level of the backlight orportions of the backlight, or colors/spectrum present in the backlightlights and/or other optical properties of the display. The energizingsignals may be produced utilizing additional sensor information from anyof brightness, spectrum, polarization of light at various points in thedisplay (e.g., at the backlight or between panels of other layers of thedisplay), or ambient viewing conditions.

In various embodiments, a controller (e.g., processing device 1055)according to the invention comprises a light field simulation moduleconfigured to determine a light field incident on one or more of thedownstream modulators. The simulation takes into account, for example,the scale of modulation and/or diffusion that takes place prior toillumination of incidence on the downstream modulators. Thus, in atleast one embodiment, the simulation takes into account two differentscales of modulation and/or diffusion in determining light incident onthe modulators. This includes, for example, consideration of localdimming and diffusion that occurs prior to illumination of the firstdownstream modulator. The simulation also takes into account any films(e.g., BEF, polarization (reference, analyzing, or clean-up) prior toillumination of the downstream modulating panels. Ultimately, thesimulation is used to determine modulation that should occur at the oneor more downstream panels and produce corresponding energizationsignals.

Such a controller is useful in both profession and consumer displayequipment. In one embodiment, the controller is installed in a medicaldevice. The controller may be configured to control a display of themedical device with regard to high resolution and contrast. Such adisplay may be designed so that viewing angle is traded for higherresolution and/or contrast. The display may be, for example, a grayscalemedical imaging device (e.g., configured to replicate film basedx-rays), or a high color high contrast (e.g., CAT scan or other images).In another embodiment, the controller is installed in a consumer displayand is configured to control the display in a manner that provides highcontrast and resolution with an industry standard viewing angle.

The invention includes enabling and/or disabling high dynamic rangefeatures on a HDR display using software. For example, the presentinvention includes packing a software system that enables HDRvideo/display capability when enabling a plug-in or activating a mode ina graphics driver. This would allow the user to switch between LDR (lowdynamic range) mode and HDR (high dynamic range) mode at the click of abutton the graphics driver UI and that would enable and disable HDRcapability on a display with any of the hardware designs that have beendescribed in this disclosure. Similarly, enabling of 2D and 3D modes maybe performed through software or plug-ins installed on a systemutilizing the described displays.

In part, the present invention has been described using the termsimage-generating panel and contrast-enhancing panel. However, it shouldbe understood that both panels generate images, and both panels impartcontrast into a final image for display. The image-generating panel, inmost described embodiments, imparting color and contrast through acombination of filtering and brightness modulation, and thecontrast-improving panel imparting contrast, or enhancing contrast, viabrightness modulation. And it should also be understood that thecontrast-improving panel could also include color filtering or othervariations of function in one or more of the contrast-improving paneland/or the image-generating panel.

In describing preferred embodiments of the present invention illustratedin the drawings, specific terminology is employed for the sake ofclarity. However, the present invention is not intended to be limited tothe specific terminology so selected, and it is to be understood thateach specific element includes all technical equivalents which operatein a similar manner. Furthermore, the inventors recognize that newlydeveloped technologies not now known may also be substituted for thedescribed parts and still not depart from the scope of the presentinvention. All other described items, including, but not limited topanels, LCDs, polarizers, controllable panels, displays, filters,glasses, software, and/or algorithms, etc. should also be considered inlight of any and all available equivalents.

Portions of the present invention may be conveniently implemented usinga conventional general purpose or a specialized digital computer ormicroprocessor programmed according to the teachings of the presentdisclosure, as will be apparent to those skilled in the computer art.

Appropriate software coding can readily be prepared by skilledprogrammers based on the teachings of the present disclosure, as will beapparent to those skilled in the software art. The invention may also beimplemented by the preparation of application specific integratedcircuits or by interconnecting an appropriate network of conventionalcomponent circuits, as will be readily apparent to those skilled in theart based on the present disclosure.

The present invention includes a computer program product which is astorage medium (media) having instructions stored thereon/in which canbe used to control, or cause, a computer to perform any of the processesof the present invention. The storage medium can include, but is notlimited to, any type of disk including floppy disks, mini disks (MD's),optical discs, DVD, HD-DVD, Blue-ray, CD-ROMS, CD or DVD RW+/−,micro-drive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs,DRAMs, VRAMs, flash memory devices (including flash cards, memorysticks), magnetic or optical cards, SIM cards, MEMS, nanosystems(including molecular memory ICs), RAID devices, remote datastorage/archive/warehousing, or any type of media or device suitable forstoring instructions and/or data.

Stored on any one of the computer readable medium (media), the presentinvention includes software for controlling both the hardware of thegeneral purpose/specialized computer or microprocessor, and for enablingthe computer or microprocessor to interact with a human user or othermechanism utilizing the results of the present invention. Such softwaremay include, but is not limited to, device drivers, operating systems,and user applications. Ultimately, such computer readable media furtherincludes software for performing the present invention, as describedabove.

Included in the programming (software) of the general/specializedcomputer or microprocessor are software modules for implementing theteachings of the present invention, including, but not limited to,calculating pixel/sub-pixel blurring of a local dimming panel,calculating color correction or characterizations, preparing imagesignals and applying them to driver and/or other electronics to energizebacklights, panels, or other devices in a display, calculating luminancevalues, interpolating, averaging, or adjusting luminance based on any ofthe factors described herein, including a desired luminance for a pixelor region of an image to be displayed, and the display, storage, orcommunication of results according to the processes of the presentinvention.

The present invention may suitably comprise, consist of, or consistessentially of, any of element (the various parts or features of theinvention) and their equivalents as described herein. Further, thepresent invention illustratively disclosed herein may be practiced inthe absence of any element, whether or not specifically disclosedherein. Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A display comprising: a backlight; an image-generating panel; acontrast-improving panel; a half wave plate positioned between the imagegenerating panel and the contrast improving panel; and a polarizingpreserving diffuser positioned between the image generating panel andthe contrast improving panel.
 2. The display according to claim 1,wherein the contrast-improving panel is placed downstream of theimage-generating panel.
 3. The display according to claim 1, wherein thecontrast-improving panel is placed upstream of the image-generatingpanel.
 4. The display according to claim 1, wherein the resolution ofthe contrast-improving panel is the same as the resolution of theimage-generating panel.
 5. The display according to claim 1, wherein theresolution of the contrast-improving panel is higher than the resolutionof the image-generating panel.
 6. The display according to claim 1,wherein the resolution of the contrast-improving panel is lower than theresolution of the image-generating panel.
 7. The display according toclaim 1, wherein the backlight comprises a direct lit backlight.
 8. Thedisplay according to claim 1 wherein the backlight comprises an edge-litbacklight.
 9. The display according to claim 1 wherein the backlight maycomprise individually controllable light sources.
 10. The displayaccording to claim 9 wherein said light source may be controlled withrespect to brightness.
 11. The display according to claim 1 wherein saidpolarization-preserving diffuser is upstream of said half-wave plate.12. The display according to claim 1 wherein saidpolarization-preserving diffuser is downstream of said half-wave plate.13. The display according to claim 1 wherein saidpolarization-preserving diffuser is combined with said half-wave plate.14. The display according to claim 1 wherein said image-generating panelis one of a group, said group comprising: a color panel and a greyscalepanel.
 15. The display according to claim 1 wherein saidcontrast-improving panel is one of a group, said group comprising: acolor panel and a greyscale panel.
 16. The display according to claim 1wherein said polarization-preserving diffuser comprises a diffuser thatsubstantially eliminates the visual moiré between said image-generatingpanel and said contrast-improving panel.
 17. The display according toclaim 1 wherein said polarization-preserving diffuser comprises adiffuser that substantially minimizes the birefringence interaction withthe polarization direction.
 18. A display comprising: a backlight; afirst stack structure, said first stack structure comprising: areflecting polarizer; an initial polarizer; an LCD panel; a finishingpolarizer; a half wave plate; and a polarization-preserving polarizer;and a second stack structure, said second stack structure furthercomprising: an initial polarizer; an LCD panel; a finishing polarizer.19. The display according to claim 18 wherein said half wave plateaffect a polarization of the image which is compatible with the initialpolarizer of the second stack structure.
 20. A display comprising: abacklight; a first LCD panel, said first LCD panel configured to receiveillumination from said backlight and modulate said illumination to forma first image and wherein first LCD further comprises a first startingpolarizer and a first finishing polarizer; a second LCD panel; saidsecond LCD panel further comprising a second starting polarizer and asecond finishing polarizer; a half wave plate, said half wave platepositioned between said first LCD panel and said second LCD panel andconfigured to receive said first image and affect a polarization of saidfirst image such that a resulting image comprises a polarization that iscompatible with said second starting polarizer; and a polarizationpreserving diffuser layer positioned between said first LCD panel andsaid second LCD panel.